Recently, a mobile communication device or a personal digital assistant (PDA) with an image-shooting function is widely used to shoot an object. When the image pickup module of the mobile communication device is used to shoot the object, the image pickup module is readily suffered from vibration because of an external force. The vibration resulting from the external force is usually referred as a handshaking action. Due to the handshaking action, the shot image is very blurred. For avoiding occurrence of handshaking, an optical image system with an anti-handshaking function has been disclosed.
Take an image pickup module of a mobile communication device for example. FIG. 1 is a schematic view illustrating an optical image system of a mobile communication device according to the prior art. The mobile communication device 1 comprises an optical image system 10. The optical image system 10 comprises a casing 100, a supporting part 101, an image pickup module 102, a vibration detecting element 103 and a swinging mechanism 104 (see FIG. 2). In addition, the optical image system 10 has an optical axis L. The supporting part 101 is arranged along the optical axis L. The image pickup module 102 is used for shooting an object to acquire an image. The image pickup module 102 is disposed on the supporting part 101, and may be swung with respect to the supporting part 101. The image pickup module 102 comprises a circuit board 1021 and a controlling unit 1022. The controlling unit 1022 is mounted on the circuit board 1021. In addition, the controlling unit 1022 is electrically connected with the vibration detecting element 103 and the swinging mechanism 104 (see FIG. 2). The vibration detecting element 103 is disposed within the optical image system 10 for detecting the tilting condition of the optical image system 10. The vibration detecting element 103 is for example a gyroscope. The swinging mechanism 104 is used for controlling a swinging action of the image pickup module 102.
Hereinafter, the detailed structure of the optical image system 10 will be illustrated with reference to FIG. 2. FIG. 2 is a schematic cross-sectional view illustrating the conventional optical image system. As show in FIG. 2, the image pickup module 102 may be swung with respect to the supporting part 101 in four directions, including a first direction D1, a second direction D2, a third direction (not shown) and a fourth direction (not shown). The third direction is perpendicular to the first direction D1. The fourth direction is opposed to the third direction. As is well known in the art, the image pickup module 102 is rotated around the pitch axis when the image pickup module 102 is swung in the first direction D1 and the second direction D2; and the image pickup module 102 is rotated around the yaw axis when the image pickup module 102 is swung in the third direction and the fourth direction. The swinging mechanism 104 comprises plural magnetic winding coils 1041, 1042 and plural magnetic elements 1043, 1044. The plural magnetic winding coils 1041 and 1042 are disposed around the image pickup module 102. The plural magnetic elements 1043 and 1044 are disposed on the casing 100, and arranged in the vicinity of the magnetic winding coils 1041 and 1042 around the image pickup module 102. The magnetic elements 1043 and 1044 are for example magnets. Each magnetic winding coil and each magnetic element cooperate with each other to control the image pickup module 102 to be swung in a specified direction. The first magnetic winding coil 1041 and the first magnetic element 1043 cooperate with each other to control the image pickup module 102 to be swung in the first direction D1. The second magnetic winding coil 1042 and the second magnetic element 1044 cooperate with each other to control the image pickup module 102 to be swung in the second direction D2. The third magnetic winding coil (not shown) and the third magnetic element (not shown) cooperate with each other to control the image pickup module 102 to be swung in the third direction D3. The fourth magnetic winding coil (not shown) and the fourth magnetic element (not shown) cooperate with each other to control the image pickup module 102 to be swung in the fourth direction D4.
Hereinafter, the operations of the optical image system with an anti-handshaking function will be illustrated in more details. Please refer to FIG. 1 again. In a case that the mobile communication device 1 is in a static status, the optical axis L of the image pickup module 102 is parallel with the optical image system 10. Meanwhile, the optical axis L is also parallel with the horizontal line. In a case that the optical image system 10 of the mobile communication device 1 is used to shoot an object but suffered from a handshaking action, the mobile communication device 1, the optical image system 10 and the image pickup module 102 are tilted in the first direction D1. Meanwhile, the optical axis L is no longer parallel with the horizontal line (see FIG. 3A). Due to the handshaking action, the image acquired by the image pickup module 102 in the tilted status is usually blurred. For preventing from acquiring the blurred image, a tilt angle compensation process is performed. For example, in a case that the mobile communication device 1, the optical image system 10 and the image pickup module 102 are all tilted in the first direction D1, an angular velocity of the optical image system 10 tilted toward the first direction D1 is detected by the vibration detecting element 103. By the vibration detecting element 103, the angular velocity is converted into an angle change amount (e.g. positive 5 degrees). Assuming that the tilt angle of the optical image system 10 tilted toward the first direction D1 is positive, the tilt angle of the optical image system 10 tilted toward the second direction D2 is negative. According to the angle change amount (e.g. positive 5 degrees), the vibration detecting element 103 issues a tilt angle compensation signal to the controlling unit 1022.
According to the tilt angle compensation signal, the controlling unit 1022 issues a negative 5-degree driving signal. In response to the negative 5-degree driving signal, the swinging mechanism 104 is controlled to make a negative 5-degree swinging action. In this situation, the image pickup module 102 is swung 5 degrees in the second direction D2 to perform a compensation swinging action. At the same time, an electric current flows through the second magnetic winding coil 1042 of the swinging mechanism 104 to generate a magnetic field. Due to the magnetic field, the second magnetic winding coil 1042 is attracted by the second magnetic element 1044, and thus the image pickup module 102 is swung 5 degrees in the second direction D2. Meanwhile, the image pickup module 102 and the optical axis L are both parallel with the horizontal line without being tilted (see FIG. 3B). Since the influence of the handshaking action on the image pickup module 102, the image acquired by the image pickup module 102 is sharp.
Ideally, the swinging mechanism 104 is controlled by the controlling unit 1022 to make a negative 5-degree swinging action. However, because of many factors, the image pickup module 102 is practically swung an angle smaller than 5 degrees in the second direction D2 (e.g. 3 degrees). In this situation, the image pickup module 102 and the optical axis L are tilted and not parallel with the horizontal line, and thus the image acquired by the image pickup module 102 is still blurred because of handshaking.